1. Field of the Invention
The invention relates generally to electronic measuring instruments and more specifically to high voltage probes used in conjunction with oscilloscopes.
2. Description of the Prior Art
High voltage oscilloscope probes allow the measurement of signals that exceed the voltage input range of oscilloscopes or other measuring instruments, such as spectrum analyzers. These measuring instruments typically have several input signal voltage ranges that vary from millivolts to tens of volts. They can be extended to measure from tens of volts to tens of thousands of volts by substituting the standard probe with a high voltage probe. For example, the Tektronix P6015 and Hewlett-Packard 1137A are commercially available high voltage probes that give a 1000:1 voltage division. Unfortunately, the prior art high voltage probes exhibit several limitations in their use.
Wider frequency response, higher input voltage capability, increased flexibility in terms of line length between the high voltage measuring point and the oscilloscope, and simpler calibration adjustments are needed. Some high voltage probes use environmentally harmful CFCs, such as Freon, to improve their insulation characteristics. Preferably, such materials should be eliminated, while at the same time improving performance levels.
Prior art high voltage probes have as many as seven adjustments for calibration. In addition, the relatively high input capacitance of prior art high voltage probes results in heavy loading of the voltage measurement point for high frequencies and requires the voltage capability of the probe to be derated above a relatively low frequency.